Article transport facilities such as one described above are installed, for example, in a ceiling area in a clean room, and are used to transport, as articles, containers for housing substrates, such as silicon substrates.
More specifically, for example, one of a plurality of travel paths is installed so as to extend by way of or along carry-in-and-out-portions of a plurality of substrate processing devices which perform different kinds of processes on the substrates. And article transport vehicles transport the articles to the plurality of substrate processing devices. And even if an article transport vehicle traveling along one travel path has stopped at a location corresponding to a carry-in-and-out portion of a substrate processing device, another article transport vehicle that was following the stopped article transport vehicle can travel past the stopped article transport vehicle by traveling along another travel path. Subsequently, the article transport vehicle that has travelled past the stopped article transport vehicle can transport its article by diverging from the another travel path and traveling into the one travel path that extends by way of the carry-in-and-out portions of the plurality of substrate processing devices.
Incidentally, each article transport vehicle has an article grip portion which can be moved vertically. And the article grip portion is vertically moved with the article transport vehicle stopped at a location corresponding to the carry-in-and-out portion of a substrate processing device when transferring an article to or from the carry-in-and-out portion of the substrate processing device.
An example of such article transport facility is disclosed in JP Publication Of Application No. 2006-282303 (Patent Document 1). In this article transport facility, the first diverging path and the second diverging path are provided at different locations in the longitudinal direction of a pair of adjacent travel paths in plan view.
Incidentally, in this Patent Document 1, an example is described in which one of the pair of adjacent travel paths is provided to extend by way of the carry-in-and-out portions of two substrate processing devices. Referring to this one of the pair as the first travel path, the example in Patent Document 1 is one in which the first diverging path that allows the article transport vehicle to diverge from this first travel path and travel into the second travel path, which is the other of the pair of the travel paths, is provided at a location that corresponds to a position between the two substrate processing devices that are adjacent to each other. And the second diverging path that allows the article transport vehicle to diverge from the second travel path and travel into the first travel path is located upstream of the substrate processing device that is located upstream of the other of the two adjacent substrate processing devices.
Because the first diverging path and the second diverging path are provided at different locations in the longitudinal direction of the pair of the adjacent travel paths in plan view in the article transport facility of Patent Document 1, there is a disadvantage that the facility designing work, in which the arrangement of the facility is finalized while determining the locations at which the first diverging path and the second diverging path should be installed, is complicated, in addition to a disadvantage that it is difficult to improve article transporting efficiency; thus there is a desire for improvements.
More specifically, it is necessary to design and set the installing locations of the first diverging path and the second diverging path that would allow the possible travel routes to be secured along which the article transport can be performed as efficiently as possible while taking into consideration various possible travel routes from article transport origins to article transport destinations. During this process, the work involved in determining the installing locations of the first diverging path and the second diverging path while taking various possible travel routes into consideration is done by comparing the case in which the first diverging path is installed with the case in which the second diverging path is installed at each location of the pair of travel paths; thus, the work was time consuming and painstaking. Thus, there was a disadvantage that the facility designing work was complicated.
In addition, in specific sections of the pair of travel paths, the travel distance may be shortened and thus the article transport efficiency may be improved by allowing both a diverging travel from the first travel path into the second travel path and a diverging travel from the second travel path to the first travel path to take place. Even in such a case, if the specific section is too short, it is difficult to improve the article transporting efficiency because only one of the first diverging path and the second diverging path can be provided.
Incidentally, the first diverging path and the second diverging path can be provided in one specific section if the specific section has sufficient length to accommodate the first diverging path and the second diverging path one after the other. However, because the travel speeds of the article transport vehicles need to be reduced at diverging locations and converging locations for safety reasons, etc., as the number of installing locations of the first diverging paths and the second diverging paths increases, the number of sections in which the article transport vehicles have to travel at low speeds increases. As a result, even when the first diverging path and the second diverging path can be provided in one specific section, it is difficult to improve article transporting efficiency.